Sunday, 27 September 2015

Bike Sizing in the Real World -- or, Making the Bike Fit YOU

Following up on previous posts about bike fit, most recently about Stack-to-Reach Ratio, I've been considering how this applies in the 'real world', specifically what lessons I might learn in relation to my own bicycles.

Let's take my Enigma Etape and my Surly Cross Check. Both are bespoke builds, that is, all the components have been chosen by me, based on my needs and preferences. It's no surprise to see both bikes sporting identical saddles, pedals and racks! However, the 'heart' of each bike is very different: the Etape is completely custom, i.e. made to measure based on my body (size / proportion / strengths / weaknesses / flexibility / range of motion) and my desire to do long rides in comfort, whereas the Cross Check is a stock frame in a stock size, a bike with a reputation for versatility but with proportions that are somewhat 'long' in reach.

Over the years, I've tended to think of these bikes in terms of their differences. Most of what I decided I wanted from the custom Enigma build was informed and shaped by my experiences with the Cross Check. My thought process was fairly linear: I don't like X about the Cross Check, so I want Y on the Enigma.

Following my knee surgery, my physiotherapist recommended that I take my Cross Check (which I'd had all of six months) and have a professional bike fitting. The verdict on the bike was that it was too long. While swapping out the stem and bars would help, it might not be enough. The weeks that followed saw many changes made to the Cross Check. The result: on the positive side, a sturdy daily ride, robust enough for Britain's incredibly poor road surfaces and able to carry heavy loads, also a stable, 'well-mannered' ride, but on the negative side, too heavy and exhausting (and still some niggles in my neck and upper back) to ride all day/night. In other words, the perfect commuter and errand bike but not the one I reach for at the weekend or for a Friday Night Ride to the Coast.

And this has been the status quo for at least three years. Last spring, I changed the saddle and pedals on the Cross Check to identical models as on the Enigma, and appreciate having exactly what I prefer now on both bikes. But no further changes were made to the way the bike fit or handled.

Then I made a discovery in August that changed everything I thought I knew about my relationship with the Cross Check.

All this time, I thought the bike was giving me every advantage possible, that my 'failures' came down to simply being a weak rider.

Not so.

For some reason, this discovery kicked off a train of thought that led me to re-evaluate the Cross Check as a potential steel back-up to the Enigma, maybe not for long day rides or touring, but certainly those longer trips where I want speed and comfort but also need to leave my bicycle locked up for a few hours out of my sight.

So now the influences have been flowing the other way, from Enigma to Surly, in more ways than mere "cosmetic" changes.

The Enigma of course is a custom frame. But the frame is only the foundation. A complete bike must be built up around it in such a way to produce a position compatible with the rider’s ‘fit coordinates’.

Bike Fit

If you’ve had a bike fit leading to a custom build, then you probably have three sets of data:

Fit co-ordinates calculated from those measurements, to identify the fairly fixed points for your feet, seat and hands, which results in your ride position.

Fit specifications can then be translated into bike specifications, in a kind of ‘reverse engineering’ process. The frame is designed with the right dimensions and proportions to enable the fit co-ordinates calculated from your bike fit to be met by the built-up bike. Ideally, you should be able to use mostly standard components to build your bike, subject to your particular preferences. (Of course some riders might need custom components if addressing a disability or severe asymmetry.) A well-designed custom bike should form a foundation onto which you can fine-tune the precise position – and tweak it slightly in any required dimension as necessary – using components that are readily available on the market. After all, most if not all components will need to be replaced as the years go by.

Frame 'blueprint' for my Engima

Frame dimensions

Of these two bicycles, one is designed to fit me.

The question is, just how different is the Cross Check from that 'ideal'?

Enigma Etape

Surly Cross Check

Effective top tube

526mm

541.8mm

Seat tube

510mm

500mm

Seat tube angle

75°

74°

Head tube angle

71°

72°

Bottom bracket drop

72mm

66mm

Chainstay length

420mm

425mm

Bottom bracket to front axle

595mm

575mm

Wheelbase

1005mm

1005.3mm

Fork rake

45mm

44mm

Trail

68mm

65mm

Stack

593mm

528mm

Reach

365mm

389.1mm

Stack to Reach Ratio

1.625

1.357

You can see from this table how different the frames (the foundations) of my two bicycles are. Could the the Cross Check be built up to replicate the position achieved on the Enigma?As it turns out, yes.

Fit solutions

Of all the data at my disposal, the fit co-ordinates are what make it possible to make a bike fit.

I never imagined how close I had come until I measured up both bikes. Based on what I found, I made a few small tweaks last weekend to the Cross Check: saddle position, then re-measured and decided to swap the 60mm stem fitted in 2011 with a 70mm stem, again with 35 degree rise.

Nothing has changed on the Enigma since the day I bought it, other than dropping the saddle height a few millimeters last May while touring in France, as a compromise between what my knees individually seem to want. (One leg wants more extension but catering to that makes the other knee unstable.)

The positions are now just about as near-identical as I think can be done.

Enigma Etape

Surly Cross Check

Saddle height

(centre of bottom bracket to top centre of saddle)

680mm

680mm

Saddle fore/aft

(relative to the bottom bracket)

-1.675cm

-1.675cm

Cockpit

(nose of saddle to front of brake hood position)

53.5cm

53.5cm

Handlebar elevation

(relative to saddle height)

+40mm

+30mm

Notes:

The two saddles are identical: Selle SMP Dynamic.

The Enigma seat post has 10 degrees setback while the Cross Check’s has zero setback.

The stem/handlebar combinations are very different, but in conjunction with the effective top tube length, saddle fore/aft position and brake lever hood size/shape, total reach adds up to the same for both bicycles. (Amazing!)

The handlebar on the Cross Check is 40cm wide while those on the Enigma are 38cm. I would swap the Enigma's if I could get exactly the same bar in size 40 but the model seems to have been discontinued altogether.

The brake levers are different: Shimano Tiagra on the Cross Check, Shimano 105 on the Enigma. The 105 brackets are longer and narrower than the Tiagra, giving quite a different feel under the hands at the hoods. I may eventually change to 105s on the Cross Check, which may mean swapping the stem out yet again.

The tyres currently fitted are Marathon Plus 700x32 (Cross Check) and Vittoria Rubino 700x32 (Enigma). The 'real world' figures for trail are therefore 66mm for the Cross Check and 71mm for the Enigma.

Here are the two bikes again, with the stack and reach frame dimensions in red and the 'real world' cockpit outlined in blue. (I drew the lines on photographs using MS Paint so their placement is not exact and proportions may appear skewed from what they are in real life.

(hmm, I've been meaning to straighten that rack for ages... must do it!)

Limitations

The key limitation in producing the same fit on the Cross Check as on the Enigma is the much shorter head tube. More height has been achieved with spacers but as more height is added, reach is shortened as the steerer (and therefore handlebars) moves close to the rider. Since the Cross Check is a relatively long bike for its size, adding as much height as possible at the front has not had enough effect on the reach to be a deal-breaker. However, the steerer tube was cut before I took delivery (against my express instructions). If it had not been, I might have another centimetre or two to play with in terms of the height of the handlebar in relation to the saddle.

All these years, struggling to find a bike that fit comfortably over longer distances, I thought reach was my 'issue'. In the process of studying bicycle geometry leading up to ordering the custom Enigma, I began to appreciate how 'stock' bicycles really were failing me more on issues of stack, not reach. Other differences… or not!

The gearing on the two bikes is comparable. The crankarms are 160mm in length. Both have triple chainsets: 48/36/26 on the Cross Check, 52/39/28 on the Enigma. The Cross Check is a 9-speed, the Enigma 10-speed but the cogs on both range from 11-36. The Cross Check therefore has lower gears. But then again it weighs 2kg more than the Enigma (with both bikes kitted out as shown in the photos – mudguards and racks included, plus empty handlebar bag on the Enigma). I went for the highest gearing on the Enigma that I could get without sacrificing the seriously sub-1:1 ratio low gears, so naturally the Enigma goes quite a bit faster on the flat (and doesn't spin out so quickly, pedalling downhill).

As for brakes, the Cross Check has Tektro cantilevers, the Enigma mechanical discs. Both stop well. Both front brakes sometimes squeal loud enough to wake the next village! (Tweaks to the adjustments usually eliminate that.)

One other small difference relates to Stance Width. While I have the same pedals on both bikes, these are available in four different spindle lengths. The standard steel spindles (as on the Cross Check) are longer than the standard titanium ones (which I have on the Enigma). I prefer the narrower stance on the Enigma. I could of course swap the pedals between the bikes! But I like the width just as it is on the Enigma and wouldn't want to widen it for the sake of narrowing the Cross Check even if the end result meant the bikes had the same stance width. (There’s also my preference to have steel parts on the steel bike and titanium parts on the titanium bike! See also racks and seat posts in this regard.)Handling / Performance

At my bike fitting with the Cross Check four years ago, I was told: "There are things we can do to make this bike fit you better i.e. make it less uncomfortable if not outright comfortable, but in doing so we may run up against the very limits of its design, with adverse effects on handling."

The main concern was putting on a short, high rise stem. No one actually spelled out what the effect on handling might be. I was fairly new to cycling and completely new to road cycling (and road bikes and the more leaned-forward position). I had nothing with which to compare the feel and handling of the Cross Check, and no experience in making such comparisons anyway. To be honest, I did not notice any difference in the bicycle as a result of swapping the stock stem for a short riser stem. I did of course notice the change in fit, although even then, the shorter reach did not make as much of an impression on me as did the change from 170mm crankarms to 160mm ones: an immediate easing of pressure in the knees, like the feeling of loosening your belt after a particularly large, filling meal!

And that remained the case for four years. In retrospect, I think I assumed that I had reached the limits of what was possible in terms of meaningful changes to the fit of the bike and that the law of diminishing returns meant further tweaks would, in the end, be a waste of time, money and energy. After the first post-bike-fitting transformation, I made various cosmetic changes over the years but fit and handling remained unaffected.

However, after August's revelation I got the measuring tape out and realised that the key areas where the Cross Check differed from the Enigma were in fact things that still had scope for adjustment.

Not only have the most recent, very small, adjustments in the Cross Check’s set up improved my position and comfort but also, quite to my surprise, changed the bike’s handling... and rather dramatically. Before, if I spent more time on one bike than on the other over a period of a few weeks, it would take 15-20 minutes to get used to the other bike again – the Cross Check being notably more ‘stable’ and the Enigma disconcertingly ‘twitchy’ when I shifted my weight, for example when looking over my shoulder or lifting one arm to indicate. Now, the stability, balance and response feel much more similar. Bearing in mind they are both high-trail bikes but did not feel equally 'stable' before, I think the most important factor in the convergence of feel and handling is the change in my weight distribution, or what the bike fitting team at the slowtwitch.com website call "(where the rider ought to be) in space".

I remember the day I collected my Enigma from the factory and rode it away. My initial impression was that I was much more stretched out than before (which surprised and alarmed me!) but over the ensuing days I realised the real change was in how much further forward my weight and centre of gravity were. Before (on the Cross Check until recently and notably also on the Surly Pacer which was my ‘good bike’ before getting the Enigma), my weight was much more over the rear of the bike, with my centre of gravity behind the bottom bracket. Now, my centre of gravity is better aligned with the bike’s own centre of gravity. Handling is much more responsive as a result and the bike feels balanced.

on the Cross Check just before the fateful bike fit - March 2011

on the Pacer - solved a few fit problems, created others - January 2013

first ride on the Enigma at the factory - October 2013

Thankfully, both bikes handle well with heavy loads on the back. Both are reassuringly stable on descents and both climb well. I climb more slowly on the Cross Check (as it's heavier) but a few days ago

I

found myself s

pontaneously out of the saddle on a hill, something I've never done before on the Cross Check but do all the time on the Enigma.

Before, the fit on the Cross Check meant pain (usually upper back and neck) after 40 miles. It’s still early days, but with the fit/position much more closely aligned to that of the Enigma and assuming all goes well over a few more weeks of commuting, then I may attempt a longer ride with it and see what my body says!

Summary

I've had the Cross Check for five years and the Enigma for two years. In the past few weeks, I've begun to appreciate how having a custom bike in the stable can serve as a template for setting up other bikes very quickly with less risk of error.

I can't afford another custom bike and there are many situations where I could not ride something so difficult, time-consuming and costly to replace should it be damaged or stolen. So I ride just about any bike, within reason. I still want to ride a bike that fits me, however! Knowing how to make changes to other bikes that are more suitable for certain rides and situations, so that these bikes are more comfortable, is hugely valuable.

It has then been possible to take an ill-fitting frame and build it up in a way that produces the right position for me.

With data about your body and a plan showing how your body needs to be positioned, you can be much better equipped to change the bike you have in order to deliver that position... or shop for a bike that does... or if necessary have one built.

4 comments:

I haven't gone into the science of a bike fit but I did build my own bike from the frame upwards to suit me more for cycling by having a light frame that was smaller than the frame on my existing bike & was built more thru trial & error to get it right. The end results was Roadrunner & is a great bike to ride, managed 100km ride on its 1st long ride & was wonderful to ride. Pics of its progress here: https://www.facebook.com/media/set/?set=a.10151925509308833.1073741843.658203832&type=1&l=ecf1760e61

I think for a long, long time I believed that if the bike wasn't perfect immediately (or close to it) then it had no chance of working for me. I think that changes to stems, saddles - the things that really can make a difference - are a great way to make a bike that is close to working be much closer to ideal. I'm slowly starting to realize that there really are ways to make almost anything work, assuming that I have the patience to play and see what works.

I'm interested to read about your real world experience on the Cross Check and to find out if the changes will make it more ideal for you. I agree that stack is often the part that I struggle with on bikes. If that isn't there, I have to figure out ways to get it to a comfortable point. I had the same issue with my CC - the fork had been cut when I bought it, which meant I couldn't get much more out of that, other than to change the stem to one with some rise.

Yes, it's still a process, no matter which way you approach it. It's very strange that I hadn't changed a single solitary thing about the Enigma. The Cross Check on the other hand has been through more regenerations than Doctor Who! And we're about to swap out the front fork - for non-fit reasons but it'll give me the opportunity to play around with that extra centimeter or two that I've haven't had.